Design And Preparation Of Novel Polyuretthanes Elastomers And Their Application Research In The Field Of 3D Printing

Fused deposition molding(FDM)is an advanced manufacturing technology that allows for the rapid fabrication of objects with complex structures without the aid of molds,thus attracting extensive research interest in various fields such as automotive,aerospace,and intelligent robotics.However,although FDM technology can manufacture objects with complex structures that are impossible with conventional manufacturing techniques,it cannot give the printed objects mechanical properties similar to those of objects fabricated with conventional manufacturing techniques,thus limiting the application of FDM printed products in the engineering field.Therefore,this paper focuses on the problems faced by FDM technology,such as poor mechanical properties of printed products,and developed novel polyurethane materials that can meet the FDM printing,and realized high-quality printing by FDM technology.Meanwhile,the development of a novel non-pneumatic tire was realized by using FDM technology,thus broadening the application scope of FDM technology,which is studied as follows:In the first part of this paper(Chapter 2),a series of novel thermoplastic polyurethane materials with excellent self-healing properties and printing adaptability were designed and prepared by introducing dynamically hindered urea bonds into the polymer chain.The self-healing properties of the material were utilized to enhance the mechanical properties of the FDM-printed products and achieve mechanical isotropy.Compared to the original printed samples,the tensile strength of the healed X-axis sample,Y-axis sample,and Z-axis sample increased by 30.8%,20.7%,and 68.1%,respectively,and the mechanical isotropy reached 90%.In addition,the self-assembly-based approach realized rapid support-free printing,avoiding the limitation of the size of the printing device on the size of the molded product,while extending the service life of the FDM printed product.In the second part of this paper(Chapter 3),a series of novel polyurethane materials with self-healing properties,intrinsic photothermal effects,and shape memory properties were designed and synthesized by introducing dynamic oxime-carbamate bonds and hydrogen bonds in the polymer chain.Based on the inherent photothermal effect and self-healing properties of the material,ondemand introduction of near-infrared(NIR)light irradiation,direct heating,and sunlight irradiation enhanced the mechanical properties of the FDM-printed products and achieved mechanical isotropy.mechanical anisotropy of the printed products can be sophistically manipulated by adjusting the self-healing conditions,providing a simple and efficient method for the construction of anisotropic products.Based on the self-healing properties of the material,support-free rapid printing and rapid healing of damaged products are realized.Moreover,4D printing was realized by printing a man-like robot based on the shape memory properties exhibited by the material.In the third part of this paper(Chapter 4),a series of novel thermosetting polyurethanes with self-healing properties and mechanically tunable properties were designed and synthesized by introducing dynamic coumarin groups and hydrogen bonds into the polymer chain.Tunable mechanical properties were achieved using reversible photodimerization and photocleavage of coumarin groups.In addition,based on self-healing properties and photodimerization of coumarin groups,FDM printing of thermosets was achieved and the mechanical properties of FDM-printed products were enhanced,while abrupt changes in rheological properties due to thermally stimulated dynamic cross-linking were avoided,ensuring the stability of the FDM printing process.Compared to the original printed samples,the irradiated X-axis,Y-axis,and Z-axis printed samples showed 88.2%,159%,and 316% improvement in tensile strength,respectively,and achieved more than 90% mechanical isotropy.In the fourth part of this paper(Chapter 5),a series of novel thermoplastic polyurethane materials with excellent self-healing properties,shape memory properties and printing adaptability were designed and prepared by introducing dynamic oxime-carbamate bonds in the polymer chain.Based on the selfhealing properties of the material,the mechanical properties of the FDM printed products were enhanced and mechanical isotropy was realized.Compared to the original printed samples,the healed HP-0°C,HP-45°,and HP-90° samples showed tensile strength increases of 35.3%,49.4%,and 143%,respectively,and mechanical isotropy of more than 96%.In addition,a novel multi-material active printing technique was proposed based on the self-assembly strategy by exploiting the self-healing properties of the materials,and multiple procedural variations of 4D printed products and support-free color 3D printing were achieved.In the fifth part of this paper(Chapter 6),the complex coupling between material properties,structural design,and NPT performance was elucidated by combining the FDM technique with NPT development,and a novel design strategy for NPTs was proposed.The results demonstrate that the radial stiffness,rolling resistance and friction properties of NPTs can be substantially adjusted through rational structural design compared to their material properties.When the material is the same with a different structure,the rolling resistance and dry friction of the NPTs decreased with increasing radial stiffness.In addition,a novel high-performance polyurethane material was designed and prepared,and pilot production was completed.Meanwhile,based on the prepared polyurethane material,the trial production of honeycomb structure NPT was completed by injection molding.The prepared NPT has a load-carrying capacity of up to 500 kg and can be driven at a speed of 80 km/h.